Member joint

ABSTRACT

A longitudinal bearer joint assembly for joining the abutting ends of two axially aligned, extruded light-metal bearer members of a front end longitudinal bearer assembly in a passenger car bodywork. The two bearer members are designed with different cross sectional profiles and wall thickness dimensions to favorably control deformation of the front end longitudinal bearer assembly. The bearer joint assembly includes a pair of half shell portions which surround and conform to the abutting ends of the two axially-aligned bearer members. The half shell portions include vertical contact surfaces which are mutually offset about a neutral axis in a vertical plane.

FIELD

The present invention relates to a joint assembly for connecting framemembers in a motor vehicle bodywork, and more particularly to a bearerjoint assembly for connecting a pair of axially aligned longitudinalbearers in a front end bearer assembly of a motor vehicle bodywork.

BACKGROUND

Customary self-supporting vehicle bodies for passenger vehicles,including the associated supporting structure, are manufactured fromsheet-metal parts. The bearer members which have hollow profiles areformed by welding together two deep-drawn metal sheets or stampings. Thebearer joints which form the connection of two bearers are typicallyformed by overlapping adjoining bearer ends and joining them at thepoints of contact with a weld seam or several spot welds.

The steel sheets used to construct such self-supporting vehiclebodyworks are typically shaped in a deep drawing process. While the diesused for shaping the steel sheets are relatively expensive, they doprovide a cost-favorable solution for mass production since they permitlarge production runs. However, in view of the high investment costs fortooling, the aforesaid process is very cost-intensive for smallerproduction runs.

A more cost-favorable solution for small production runs is known, forexample, from European Patent document EP 0 146 716. This documentdiscloses a vehicle body for a passenger car comprising a bearingstructure assembled from a plurality of hollow section frame memberswhich are joined together by nodes or junction elements. The hollowsection frame members are formed as extruded light-alloy (aluminum)sections and the junction elements are formed as light- alloy castings.In addition to being a more cost-favorable solution for small productionruns, a light-alloy bodywork of the type disclosed in EP 0 146 716weighs less and is more resistant to corrosion than a sheet metalbodywork.

In the case of such a light-alloy bodywork, the front end longitudinalbearer assembly is assembled from bearer members of different profiles.The bearer members are joined by inserting an end of a first bearermember within a receiving end of a second bearer member or by placingthem against one another in positive engagement after which they arethen fixed in place by welding. A longitudinal bearer member joint issubject to very high loads, particularly during frontal impact.Accordingly, this joint is designed with suitably large dimensions toensure adequate rigidity and strength.

German patent document DE 38 11 427 discloses a contact joint forconnecting two axially aligned hollow section longitudinal bearermembers, each having the same polygonal cross-sectional profile, whereinthe adjoining end of one bearer member is notched for fitted insertionwithin the receiving adjoining end of the other bearer member. Adhesiveis applied to the notched surfaces prior to insertion. A disadvantagehere, however, is that only longitudinal bearer members of the samecross-sectional profile may be joined by such a technique.

French patent document FR 775 182 discloses a sheet metal clam shelljunction element for connecting the ends of four tubular longitudinalmembers at right angles to one another. The clam shell junction elementcomprises a top and bottom half shell portions. When assembled, the topand bottom half shell portions fully enclose the adjoining bearer memberends and are welded together at mating edges thereof. The resulting weldseam is disposed in a horizontal plane at the approximate middle of theassembly and therefore lies disadvantageously in a zone subject to veryhigh loads.

THE INVENTION OBJECTS

It is therefore an object of the present invention to provide a simpleand strong longitudinal bearer Joint assembly for joining the abuttingends of two axially aligned longitudinal bearer members in a front endbearer assembly of a vehicle bodywork which overcomes the problems ofthe prior art.

It is another object of the invention to provide a longitudinal bearerJoint assembly of the type described wherein the cross-sectionalprofiles of the longitudinal bearer members to be connected by the jointassembly are specially dimensioned to favorably control the extent ofdeformation to the front end bearer assembly during a frontal impact tofacilitate simple and low cost repairs.

Other and further objects will become evident from the following writtendescription, drawings and appended claims.

DRAWINGS

FIG. 1 is an exploded perspective view of a compound longitudinal bearerassembly showing a longitudinal bearer joint assembly constructed inaccordance with one embodiment of the present invention.

SUMMARY

The invention concerns an improved longitudinal bearer joint assemblyfor connecting the abutting ends of two axially aligned longitudinalbearer members in a front end bearing assembly of a vehicle bodywork.The longitudinal bearer members are designed as light-metal (i.e.aluminum alloy) extruded sections and the joint assembly comprises apair of shell portions designed as light-metal castings.

The cross-sectional profiles of the abutting longitudinal bearer membersare selectively dimensioned such that the first or more forwardlydisposed longitudinal bearer member is less rigid and is a weaker memberin compression than the second or more rearwardly disposed bearermember. Such selective dimensioning of the two adjoining longitudinalmembers results a step change or transition of the cross-sectionalprofile dimension at the junction between the two longitudinal bearermembers. That is, the second rearwardly disposed bearer members isgenerally larger in cross-section and has a greater wall thicknessdimension than the first, forwardly disposed bearer member.

The interior surfaces of the half shell portions are matched toconformingly fit around the exterior surfaces of the longitudinal bearermembers at the step change. The dividing line between the two half shellportions defining their mutual contact surfaces is oriented in avertical plane.

The above described extruded light-metal compound longitudinal bearerassembly ensures that, in the event of a minor (i.e., low energy)frontal impact, only the first, more forwardly disposed (and less rigid)bearer member of the longitudinal bearer assembly will deform, while thesecond, rearwardly adjoining bearer member along with the other frameparts and units connected thereto will not suffer damage. As a result,collision damage to the front end is minimized so that for minor frontalcollisions, it is usually only necessary to replace the first, moreforwardly disposed bearer member during a repair.

The design of the longitudinal bearer joint via half shell portions isparticularly well suited for connecting the adjoining ends of axiallyaligned bearer members of different cross-sectional profiles, since itis a simple matter to incorporate added wall thicknesses to the halfshell portions where needed in the region of the step change to ensureadequate strength. Further, the design of the half shell portions ascastings makes it simple to produce such matched wall thicknessvariations and profile transitions.

An inexpensive and suitable construction for such a compoundlongitudinal bearer assembly includes a first bearer member formed as asimple cylindrical tube and a second bearer member designed as anextruded-section bearer having a polygonal cross-section for higherstiffness.

In contrast to a longitudinal bearer joint which is formed as a singlepiece casting, there are no casting bevels in the seam region and nosliders or shims are required in the production process. Although here,as in an insertion joint, a complete connection is possible, theabove-mentioned disadvantages associated with the use of insertionjoints, and particularly the alignment and fitting problems associatedwith alignment and connection of the last bearer members, are notpresent, because the half shell portions can be attached horizontally tothe direction of the bearer members. The overall result is a lesscomplicated construction than the prior art.

Another advantage of the dual half shell Joint construction of thepresent invention, especially in comparison to insert joints, is thattolerances in the half shell portions can be better reconciled.

In a longitudinal bearer assembly which comprises two axially adjoiningbearer members, the least critical loading region lies in the vicinityof the vertical axial plane or the so called "neutral axis".Accordingly, the strength of the longitudinal bearer joint may befurther increased by aligning the mutual contact surfaces of the twohalf shell portions in the vicinity of the neutral axis of thelongitudinal bearer assembly. In this way, weld or adhesive bondingseams at the contact surfaces of the shell portions would be located inregions of the longitudinal bearer assembly which experience the leastamount of loading forces and stress.

A further increase in strength of the longitudinal bearer joint assemblymay be realized by offsetting the mutual contact surfaces of the halfshell portions in the circumferential direction relative to the axiallyaligned and adjoining bearer members. In particular, offsetting themutual contact surfaces of the half shell portions such that they lie onopposite sides of the neutral axis advantageously influences the forcecharacteristic in the longitudinal bearer joint assembly.

Suitable joining techniques such as welding or adhesive bonding may beemployed to secure the half shell portions to the longitudinal bearermembers and to one another at their regions of mutual contact.

Depending upon the circumstances, material and weight savings may berealized by providing the half shell portions with openings orperforations. However, care must be used in the number and size of theopenings so as not to compromise the strength of the resulting jointconnection.

A positive engagement between the longitudinal bearer members can beproduced in the axial direction by forming ribs or supports in the halfshell castings. Such an axial positive engagement has astrength-increasing effect for a longitudinal-member arrangementcomprising two axially aligned adjoining bearer members.

Further, where the half shell portions are formed as castings, they canbe configured such that they are sufficiently strong to supportadditional members. For example, mountings or support struts may beformed integral with one or both of the half shell portions during thecasting process.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what wepresently believe is the best mode of carrying out the invention.

FIG. 1 shows a longitudinal bearer joint assembly 1 constructed inaccordance with one embodiment of the present invention. Thelongitudinal bearer Joint assembly 1 shown represents one of a pair oflongitudinal bearer joint assemblies typically located in the forwardregion of a passenger vehicle bodywork (not shown). The longitudinalbearer assembly 1 comprises a first, forwardly disposed bearer member 2and a second, rearwardly disposed bearer member 3 axially adjoinedthereto. The first bearer member 2 is a cylindrical tube comprised of analuminum alloy. The second bearer member 3 is an extruded sectiondesigned as a hollow section, and is likewise comprised of an aluminumalloy. The second bearer member 3 preferably has a somewhat largercross-sectional profile than the first bearer member and is polygonal incross-section with straight external surface portions. The first bearermember 2 is designed to be less stiff than the second bearer member 3such that only the first bearer member 2 will experience deformationduring a low energy frontal impact such that the second bearer memberalong with other frame elements connected thereto remains undeformed.

The first bearer member 2 and the second bearer member 3 are alignedwith one another along a common longitudinal axis A--A and abut oneanother at their respective end regions 5 and 6.

The abutting ends 5 and 6 of bearer members 2 and 3 are secured in placeby a clam shell-type joint enclosure comprising of a first half shellportion 7 and a second half shell portion 8.

The two half shell portions 7 and 8 include semi-annular contactsurfaces 9 and 10 at their forwardly disposed ends which, when broughttogether, surround and positively grip the cylindrical end region 5 ofthe first bearer member 2. In addition, vertical contact surfaces 9a and9b of the half shell portion 7 matingly engage the coordinately alignedvertical contact surfaces 10a and 10b of half shell portion 8.

Similarly, at the rearwardly disposed ends of the half shell portions 7and 8, that is in an area which points towards the middle of the vehicleor towards the second, rearwardly disposed bearer member 3, each halfshell portion 7, 8 contains inner contact surfaces 12 and 13,respectively, which are shaped to conformingly and positively grip theend region 6 of the second bearer member 3 when the shell parts 7 and 8are assembled. In this area too, vertical parting faces 14a and 14b ofhalf shell portion 7 rest against coordinate vertical parting faces 15aand 15b of half shell portion 8. As is clearly seen in FIG. 1, thevertical parting faces 9a, 9b and 14b do not lie in one axial verticalplane but are preferably offset relative to one another in thecircumferential direction.

The second half shell portion 8 is provided with a bottom plate 15 whichextends beneath a bottom flat wall of the bearer member 8 and includes aterminal end 15a which rests against contact surface 12 of the firsthalf shell portion 7.

Additional support members may be formed integral with one or both ofthe cast light metal half shell portions 7 and 8 during the castingprocess. For example, a connecting support member 16, which represents aspring-strut mounting, is shown formed integral with the second halfshell portion 8.

To reduce weight and material, one or both half shell portions 7 and 8may contain openings or perforations in non-critical regions. Forexample, such an opening 17 is provided in a central area of the sidewall of the second half shell portion 8. One or more axial ribs 11 (inphantom) may be provided to the inner walls of the half shell portions7, 8 to promote a positive engagement between the longitudinal bearermembers.

The bearer arrangement shown is assembled as follows:

The two bearer members 2 and 3 are placed against one another in axialalignment by their abutting end regions 5 and 6. The half shell portions7 and 8 are then fitted around the adjoining end regions 5 and 6. Thehalf shell portions 7 and 8 are then welded together at their mutuallycontacting surfaces. At the same time, the accessible outer rims of eachcontact surface are welded to the exterior surface of the adjacentbearer member. Alternatively, an adhesive bonding technique may beemployed to secure the mating contact surfaces of each half shellportions 7 and 8 and the bearer member contact surfaces to theirrespective bearer members 7 and 8. The resulting connection provides astrong and positive locking longitudinal bearer joint at the steptransition between two bearer members of different cross-sectionalprofiles.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. We therefore wish our invention to bedefined by the scope of the appended claims as broadly as the prior artwill permit, and in view of the specification if need be.

We claim:
 1. A longitudinal bearer joint assembly in a front end bearingstructure of a motor vehicle bodywork comprising in operativecombination:a) a longitudinal bearer assembly including:i) a firstextruded light metal bearer member of a first cross sectional profileand having a front end and a rear end; ii) a second extruded light metalbearer member of a second cross sectional profile and having a front endand a rear end; iii) said second bearer member is disposed axiallyaligned with and behind said first bearer member with said second bearermember front end in abutment with said first bearer member rear end; iv)said second cross sectional profile is greater than said first crosssectional profile such that said second bearer member is stiffer incompression than said first bearer member and there is a step change inprofile dimension at the region of abutment between said first andsecond bearer members; b) a joint assembly for joining said first andsecond bearer members at said step change, said joint assemblyincludes:i) a pair of matingly engagable cast light metal half shellportions each having vertically oriented mutual contact surfaces; ii)each of said half shell portions having a concave inner surface whichconforms to exterior surfaces of said first and second bearer members atsaid step change; and iii) at least one of said half shell portionsincludes an integral support member extending from an exterior surfacethereof, said support member for attachment with other frame elements;and c) means for securing said half shell portion to said first andsecond bearer members and to each other adjacent said mutual contactsurfaces.
 2. A longitudinal bearer joint assembly as in claim 1 whereinat least one of said half shell portions includes a central opening in aside wall thereof.
 3. A longitudinal bearer joint assembly as in claim 1wherein:a) said first cross sectional profile of said first bearermember defines a generally cylindrical tube; and b) said second crosssectional profile of said second bearer member defines a polygonal tube.4. A longitudinal bearer joint assembly as in claim 1 wherein at leastone of said half shall portions includes at least one rib memberdisposed along the corresponding concave inner surface thereof tofacilitate a positive axial engagement between said first and secondbearer members.
 5. A longitudinal bearer joint assembly as in claim 1wherein said securing means comprises weld connections.
 6. Alongitudinal bearer joint assembly as in claim 1 wherein said securingmeans comprises glue adhesive connections.
 7. A longitudinal bearerjoint assembly as in claim 1 wherein:a) said vertically oriented mutualcontact surfaces of said half shell portions are mutually offset about aneutral axis of said longitudinal bearer assembly.
 8. A longitudinalbearer joint assembly as in claim 7 wherein at least one of said halfshell portions includes a central opening in a side wall thereof.
 9. Alongitudinal bearer joint assembly as in claim 8 wherein:a) said firstcross sectional profile of said first bearer member defines a generallycylindrical tube; and b) said second cross sectional profile of saidsecond bearer member defines a polygonal tube.
 10. A longitudinal bearerjoint assembly as in claim 9 wherein at least one of said half shallportions includes at least one rib member disposed along thecorresponding concave inner surface thereof to facilitate a positiveaxial engagement between said first and second bearer members.
 11. Alongitudinal bearer joint assembly as in claim 10 wherein said securingmeans comprises weld connections.
 12. A longitudinal bearer jointassembly as in claim 10 wherein said securing means comprises glueadhesive connections.
 13. A longitudinal bearer joint assembly as inclaim 7 wherein:a) said first cross sectional profile of said firstbearer member defines a generally cylindrical tube; and b) said secondcross sectional profile of said second bearer member defines a polygonaltube.
 14. A longitudinal bearer joint assembly as in claim 13 wherein atleast one of said half shell portions includes at least one rib memberdisposed along the corresponding concave inner surface thereof tofacilitate a positive axial engagement between said first and secondbearer members.
 15. A longitudinal bearer joint assembly as in claim 14wherein said securing means comprises weld connections.
 16. Alongitudinal bearer joint assembly as in claim 14 wherein said securingmeans comprises glue adhesive connections.
 17. A longitudinal bearerjoint assembly as in claim 14 wherein at least one of said half shallportions includes at least one rib member disposed along thecorresponding concave inner surface thereof to facilitate a positiveaxial engagement between said first and second bearer members.